JPH07208708A - Recuperative burner - Google Patents

Abstract

PURPOSE:To compact a burner and increase heat transfer efficiency by providing a space, enough to establish straight steel tubes, between a combustion cylinder and an outer cylinder. CONSTITUTION:Two-stage flat spaces 9, 10 are formed at the closed end of an outer cylinder 4 for inducing exhaust gas by a bottom plate 6 and two sheets of parallel bulkheads 7, 8 while a plurality of straight steel tubes 14, whose tip end is closed and whose interior is divided into a sending passage 12 and a returning passage 13 through a partitioning wall 11, are established between a combustion cylinder 2 and the outer cylinder 4 so that the base ends of them are penetrated through both bulkheads 7, 8. The sending passage 12 and the returning passage 13 are communicated with two-stage spaces 9, 10 respectively while the base end of the combustion cylinder 2 is communicated with the space 10 of the side of returning passage 13. According to this method, heat transfer area can be secured sufficiently and the burner can be compacted while the heat transfer efficiency can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called recuper burner for recovering exhaust heat by exchanging heat between combustion air and exhaust gas.

[0002]

2. Description of the Related Art FIG. 3 shows the structure of a conventional recuperative burner. An outer cylinder 4 for recovering exhaust heat is provided around a combustion cylinder 2 of a burner body 3 and circulates in a furnace to discharge it to a flue. The thermal efficiency was improved by preheating the combustion air with the heat of the exhaust gas generated. However, in this configuration, since heat exchange between the exhaust gas and the combustion air is performed only through the inner wall surface of the outer cylinder 4 and the combustion cylinder 2, the heat transfer area cannot be increased so much,
There is a drawback that the heat recovery efficiency is limited.

[0003]

The multi-body recuperative burner shown in FIG. 4 has been developed to solve the above-mentioned drawbacks, and the burner body 3 and the exhaust heat recovery heat exchanger A are separately provided adjacent to each other. And a heat transfer pipe 19 through which combustion air passes is provided in the exhaust heat recovery cylinder 18. If you do this,
Since it is not necessary to provide the burner main body 3 in the exhaust heat recovery cylinder 18, by using this space for the heat transfer pipe 19,
While it has the advantage that the heat transfer area between the exhaust gas and the combustion air can be increased to improve heat recovery efficiency, it requires more complicated handling such as mounting on the furnace wall compared to the single-cylinder type, and also has a heat transfer effect. The pipe 19 cannot be formed by spirally winding it like a thin pipe for liquid, and it is necessary to weld the large diameter pipe 19a and the annular pipe 19b as shown in FIG. Therefore, there is a problem that the manufacturing cost is high, and the welded joint is easily damaged due to thermal stress due to the difference in thermal expansion between the respective parts, and the durability is low. Further, since the recupe burner uses preheated air, there is a problem that the flame temperature rises as much and the NOx concentration in the exhaust gas becomes high. An object of the present invention is to solve the above-mentioned problems and to provide a single-body type recuperative burner that is compact, has high heat recovery efficiency, and is capable of reducing NOx.

[0004]

As shown in FIG. 1, a recuperative burner according to a first aspect of the present invention is provided with a burner body 3 composed of a burner nozzle 1 and a combustion cylinder 2 surrounding the burner nozzle 1 concentrically with the burner body 3. Outer cylinder 4 for exhaust gas suction with a bottomed cylindrical shape
The exhaust gas that is penetrated through the central portion of the outer cylinder 4 and is sucked from the open end of the outer cylinder 4 is discharged from the discharge port 5 provided on the side wall near the closed end of the outer cylinder, and at the same time, the closed end of the two plates parallel to the bottom plate 6 Two-tiered flat spaces 9 and 10 are formed by the partition plates 7 and 8, the front end is closed and the inside is divided by the partition wall 11 into the outward path 12 and the return path 13.
A plurality of straight tubular steel pipes 14 divided into and are erected between the combustion cylinders 2 and the outer cylinders 4 by penetrating the both end plates through the partition plates 7 and 8, and the forward path 12 and the return path 13 are respectively described above. The two spaces 9 and 10 are communicated with each other, and the base end of the combustion tube 2 is communicated with the space 10 on the return path side.

Further, in view of the fact that the NOx concentration in the exhaust gas becomes higher as the temperature of the preheated air becomes higher, the exhaust gas suction hole 15 is formed in the side wall at the base end of the combustion cylinder 2. By forming the ejector 17 by the projecting piece 16 projecting from the inner wall surface of the combustion cylinder 2 immediately upstream of the exhaust gas suction hole 15, a part of the exhaust gas is mixed with the combustion air for recirculation. Thus, the flame temperature is lowered to reduce the generation of NOx.

[0006]

According to the first aspect of the invention, the steel pipe 14 disposed between the combustion cylinder 2 and the outer cylinder 4 is closed at its tip and the inside is divided into the outward path 12 and the return path 13 by the partition wall 11. Since each of them can independently exhibit the function of heat transfer, the connecting pipe 16 as shown in FIG. 4 is not required between the steel pipes 14 and the structure is simple and narrow. Since many steel pipes can be easily lined up in a place, it has become possible to improve heat efficiency by installing a heat transfer pipe in a single-cylinder type recupe burner as in the double-cylinder type. Further, since each steel pipe 14 is welded and fixed only at the base end on the low temperature side, unlike the heat transfer member in the conventional example of FIG. Since the heat member can be made of an inexpensive general-purpose material such as the straight steel pipe 14, the flat partition wall 11 and the partition plates 7 and 8, the cost can be reduced.

Further, according to the second aspect of the invention, a part of the exhaust gas is burned by a very simple structure in which the exhaust pipe 15 is provided with the exhaust gas suction hole 15 and the projecting piece 16 is provided on the inner wall surface thereof. Therefore, the NOx can be reduced without increasing the size and adding special auxiliary devices as in the conventional case.

[0008]

FIG. 1 shows an embodiment of a recuperative burner according to the present invention, in which a tip of an outer cylinder 4 for sucking exhaust gas is open to an inner wall surface of a furnace, and a burner body 3 provided at the center thereof. A flame is ejected from the combustion cylinder 2 of.
The high temperature exhaust gas flowing from the furnace into the outer cylinder 4 heats the combustion air passing through the inside by the inner wall surface of the outer wall 4 and the surface of the steel pipe 14, and then is discharged from the discharge port 5 to the exhaust duct. And the heated air is in the space 10 on the return path side.
Is supplied to the combustion cylinder 2 through. At the closed end of the outer cylinder 4, two partition plates 7 and 8 having a plurality of pipe insertion holes are provided in parallel with the bottom plate 6, and the partition plates 7 and 8 and the bottom plate 6 are connected to each other. By this, two flat spaces 9 and 10 are formed,
Combustion air is supplied from the blower to the outward space 9 and the proximal end of the combustion tube 2 is opened in the center of the return space 10 so that heated air is supplied to the combustion tube 2. Has become. The space between the combustion tube 2 and the outer tube 4 is equiangularly spaced at the tip and the inside is divided by the partition wall 11 into the forward path 12.
And 6 straight tubular steel pipes 14 divided into two
However, the base end portion of the steel pipe 14 is welded to the pipe insertion holes of the two partition plates 7 and 8 to be erected, and the outward passage 12 and the return passage 13 communicate with the two-stage spaces 9 and 10, respectively. Corresponding parts are cut in D shape.

Further, a plurality of exhaust gas suction holes 15 are formed in the side wall of the base end portion of the combustion cylinder 2, and these exhaust gas suction holes 15 are formed.
On the upstream side in the immediate vicinity of, a truncated cone-shaped projecting piece 16 is projected from the inner wall surface of the combustion cylinder 2, and an ejector nozzle 17 is formed between this projecting piece 16 and the peripheral surface of the burner nozzle 1. Due to the action of the ejector 17, a part of the exhaust gas is sucked into the combustion cylinder 2 from the exhaust gas suction hole 15 and mixed with the combustion air, thereby reducing the NOx. Figure 2
Is a furnace temperature 1000 ℃, preheat air temperature 330 ℃,
At the time of rated combustion with a calorific value of 100,000 kcal / h, the exhaust gas content rate (FGR) was changed by changing the inner diameter of the ejector nozzle, and the NOx concentration at that time was measured. It is shown that it can be reduced to 1/3.

[0010]

According to the present invention, as described above, the combustion cylinder 2
Since it suffices if there is a gap between the outer tube 4 and the outer tube 4 so as to stand the straight tubular steel tube 14, it is not necessary to increase the outer diameter of the outer tube 4 too much. However, since each steel pipe 14 is independent and there is almost no pressure loss of the exhaust gas flow, it is possible to secure a sufficient heat transfer area even though it is a single cylinder type, and therefore to provide a compact single cylinder type recuperative burner with high heat transfer efficiency. Moreover, since each steel pipe 14 is welded and fixed only at the low temperature base end portion, there is no risk of damage due to thermal stress applied to the welded joint unlike the conventional heat transfer member. Therefore, there is an advantage that the durability can be improved, and the heat transfer member can be composed of only inexpensive general-purpose materials such as a straight steel pipe, a flat partition wall 11 and partition plates 7 and 8. Can be reduced That. Further, by forming the exhaust gas suction hole 15 in the combustion cylinder 2 and forming the ejector nozzle 17 by providing the projecting piece 16 on the inner wall surface thereof, a part of the exhaust gas can be mixed with the combustion air with a very simple structure. You can
As a result, there is an advantage that the NOx can be reduced without increasing the size and adding special auxiliary devices as in the conventional case.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the present invention.

FIG. 2 is a graph showing the NOx reduction effect according to the above.

FIG. 3 is a vertical sectional view of a conventional example.

FIG. 4A is a vertical sectional view of another conventional example, and FIG.

[Explanation of symbols]

 1 Burner Nozzle 2 Combustion Cylinder 3 Bottom Plate 4 Outer Cylinder 5 Discharge Port 6 Bottom Plate 7 Separator 8 Separator 9 Outward Path Space 10 Return Path Side Space 11 Partition Wall 12 Outgoing Path 13 Return Path 14 Steel Pipe 15 Exhaust Gas Suction Hole 16 Projection Piece 17 Ejector Nozzle 18 Discharge Heat recovery cylinder 19 Heat transfer pipe A Heat exchanger

Claims (2)

[Claims] 1. A burner main body composed of a burner nozzle and a combustion cylinder around the burner nozzle is penetrated through a central portion of a bottomed cylindrical exhaust gas suction outer cylinder concentrically provided with the burner main body, and from an open end of the outer cylinder. The sucked exhaust gas is discharged from the exhaust port provided on the side wall near the closed end of the outer cylinder, and two closed plates are connected to the combustion air source and the gas burner at the closed end by two partition plates parallel to the bottom plate. A straight tubular tube that forms a flat space of which the tip is closed and the inside is divided into a forward path and a return path by a partition wall. A recuper burner comprising a plurality of standing tubes, the forward path and the return path communicating with the two-stage spaces, and the base end of the combustion cylinder communicating with the return path space. 2. An exhaust gas suction hole is formed in a side wall of a base end portion of the combustion cylinder, and an ejector is formed by a projecting piece projecting on an inner surface of the combustion cylinder on an upstream side in the immediate vicinity of the exhaust gas suction hole. The recuperative burner according to claim 1, wherein a part of the exhaust gas is mixed with the combustion air.